1. Field of the Invention
The present invention relates to an alignment apparatus, exposure apparatus, and device manufacturing method.
2. Description of the Related Art
As discussed in Japanese Patent Laid-Open No. 2003-22960, there has conventionally been proposed an alignment apparatus (stage apparatus) using linear motors.
As discussed in Japanese Patent Laid-Open No. 2001-203140, there has also conventionally been proposed an alignment apparatus (stage apparatus) using electromagnets.
As shown in FIG. 19, an alignment apparatus 700 of Japanese Patent Laid-Open No. 2003-22960 interposes linear motors 741 and 742 between a fine moving stage 710 and a coarse moving stage 730. More specifically, in the linear motors 741 and 742, the Lorentz force acts between linear motor movable elements 741a and 742a attached to the fine moving stage 710 and linear motor stators 741b and 742b attached to the coarse moving stage 730. This makes it possible to drive the fine moving stage 710 in the horizontal direction and vertical direction relative to the coarse moving stage 730.
However, the alignment apparatus 700 of Japanese Application Publication No. 2003-22960 has an arrangement in which the linear motor movable element 742a readily vibrates the fine moving stage 710 because the linear motor movable element 742a is cantilevered to the fine moving stage 710. The point of impact of a control force, which acts on the fine moving stage corresponds to the position where each linear motor is set. When a linear motor, which drives the fine moving stage in the vertical direction is positioned at the edge of the fine moving stage, its elastic mode is readily excited. For these reasons, the fine moving stage 710 may deform to result in a decrease in its alignment accuracy.
As shown in FIG. 20, an alignment apparatus 800 of Japanese Patent Laid-Open No. 2001-203140 interposes electromagnets between a fine moving stage 810 and a coarse moving stage 830. More specifically, a magnetic attraction force acts between electromagnets 841a, 842a, 843a, and 844a attached to the fine moving stage 810 and iron pieces 841b, 842b, 843b, and 844b attached to the coarse moving stage 830. This makes it possible to drive the fine moving stage 810 in the vertical direction relative to the coarse moving stage 830.
However, the alignment apparatus 800 of Japanese Patent Laid-Open No. 2001-203140 attaches the electromagnets 841a, 842a, 843a, and 844a to the neighborhoods of the four corners of the fine moving stage 810. When a driving force in the vertical direction is transmitted to the fine moving stage 810, the fine moving stage 810 may locally deform. This may decrease the alignment accuracy of the fine moving stage 810.